Links :

RPM are available in Fedora repository (updates-testing) for Fedora ≥ 13 and rawhide.

RPM are also available in remi repository, with php-5.3.3, for fedora core 6 to fedora 12, Enterprise Linux 4 and 5 (RHEL or CentOS).

Installation with YUM:
yum --enablerepo remi install php-pecl-memcache

The memcached PHP Sessions article (which need a translation) will show you how to configure the PHP session handler.

This package is part of Red Hat Enterprise Linux 6 (so, removed from EPEL-6)